1. Technical Field
The present invention relates to a solid-state image pickup element, a solid-state image pickup device and a production method therefor, and more particularly to a CCD solid-state image pickup element, a CCD solid-state image pickup device and a production method therefor
2. Background Art
In a conventional solid-state image pickup device (solid-state image sensor) for use in a video camera and others, a plurality of photodetection elements are arranged in a matrix array, and a vertical charge-coupled device (VCCD) is provided between adjacent columns of the photodetection elements to read signal charges generated in an associated one of the adjacent columns of photodetection elements.
A structure of the conventional solid-state image pickup device will be described below (see, for example, the following Patent Document 1). FIG. 1 is a sectional view showing a unit pixel of the conventional solid-state image pickup device. A photodiode (PD) in each unit pixel is comprised of an n-type photoelectric conversion region 13 formed in a p-type well region 12 formed in an upper region of an n-type semiconductor substrate 11, to serve as a charge storage layer, and a p+-type region 14 formed on the n-type photoelectric conversion region 13.
An n-type CCD channel region 16 is also formed in the p-type well region 12 in the form of an n-type impurity-doped region. A portion of the p-type well region 12 between the n-type CCD channel region 16 and the photodiode from which signal charges are read out to the n-type CCD channel region 16 is formed as a p-type impurity-doped region to provide a read channel. Thus, signal charges generated in the photodiode are temporarily stored in the n-type photoelectric conversion region 13, and then read out to the n-type CCD channel region 16 via the read channel.
Further, a p+-type element isolation region 15 is provided between the n-type CCD channel region 16 and another adjacent photodiode. Based on the p+-type element isolation region 15, the n-type CCD channel region 16 is electrically isolated from the adjacent photodiode, and the n-type CCD channel region 16 are isolated from another adjacent n-type CCD channel region.
A transfer electrode 18 is formed on a surface of the semiconductor substrate through a Si oxide film 17 to extend in a horizontal direction and pass through between the photodiode and the adjacent photodiode. Thus, in the solid-state image pickup device, when a read signal is applied to a selected one of the transfer electrodes 18, the read channel located just below the selected transfer electrode 18 is effected to allow signal charges generated in the photodiode associated with the read channel to be read out to the corresponding n-type CCD channel region 16 therethrough.
A metal shield film 20 is formed on the surface of the semiconductor substrate having the transfer electrodes 18. The metal shielding film 20 has a plurality of metal-shield-film openings 24 each provided as a light transmission portion on a photodiode-by-photodiode basis to transmit therethrough light to be received by the p+-type region 14 serving as a light-receiving section.
[Patent Document 1] JP 2000-101056A
As above, in the conventional solid-state image pickup element, the photodiode (PD), the read channel, the n-type CCD channel region and the p+-type element isolation region are formed in one plane, and thereby there is a limit to an increase in ratio of a surface area of a light-receiving section (photodiode) to the overall surface area of one pixel. It is therefore an object of the present invention to provide a solid-state image pickup element capable of reducing an area of a read channel to increase a ratio of a surface area of a light-receiving section (photodiode) to the overall surface area of one pixel.